Hello, Welcome to the magical world of health care, I went through your query, and first stop the magnesium you are taking unless it cause further damage, There are various reasons for these cramps and first is to find out the cause you have, Deficiency of calcium, phosphorous, magnesium, Potassium, and essential vitamins can all cause cramps, moreover thyroid kidney and arterial diseases can also cause it. so please see a physician and get yourself evaluated, no empirical treatment should be taken without guidance as this could be harmful. I hope my advice would have been useful, in decision making regarding your treatment, still if you have any clarifications or doubts feel free to contact back. Thanks.